No start. Window,radio,sunroof,door locks don't work

That was already checked. We have had two mechanics look at it. One told us it needed an ECM. So we bought one an that wasn't the problem. The other one said the ignition switched so he changed that out and that didn't work either.

Try alldatadiy.com , they might have the circuit info you need to do the proper tests. It turns over , but wont start , right? Have you verified no-spark , or no fuel (pressure or injector pulse)? I presume the ECM was verified , before replacement , by hooking to a scanner and monitoring what you could even though it won't start? The ignition switch was TESTED for continuity between appropriate pin contacts at the specific positions , before replacement? Tell me what DOES work...Horn , headlights power seats , heater blower motor? Dome light?

It does not turn over. We had GM mechanics look at it and yes they used scanners on it. The motor will run for a few seconds if you jump the starter from the fuse box. I'm no mechanic but it seems like the factory alarm is on. When you put the key in it is states driver unknown. It used to say driver 1 or driver 2. We got frustrated and just brought it home. The horn,headlights, heater blower,flashers are the only things that work. They did change the main fuse and of course that didn't work either.